A144658 a(n) = Sum_{i=1..n} Sum_{j=1..n} Sum_{k=1..n} (i+j+k)!/(i!*j!*k!).

0, 6, 222, 5052, 109512, 2432448, 55611294, 1301187912, 30992726652, 748573575780, 18283412752602, 450657126652626, 11192820097106112, 279787295335659972, 7032532241701837758, 177611430241032329568

Offset: 0

Author

N. J. A. Sloane, Jan 30 2009

Keywords

• nonn

Links

• Seiichi Manyama, Table of n, a(n) for n = 0..100

Crossrefs

Cf. A144511.

Programs

Mathematica

Table[Sum[Sum[Sum[(i+j+k)!/i!/j!/k!,{i,1,n}],{j,1,n}],{k,1,n}],{n,1,30}]

PARI

{a(n) = sum(i=1, n, sum(j=1, n, sum(k=1, n, (i+j+k)!/(i!*j!*k!))))} \\ Seiichi Manyama, May 19 2019

PARI

{a(n) = sum(i=3, 3*n, i!*polcoef(sum(j=1, n, x^j/j!)^3, i))} \\ Seiichi Manyama, May 19 2019